This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 120 |
| 6 | 726 |
| 7 | 5040 |
| 8 | 40410 |
| 9 | 362881 |
| 10 | 3630840 |
| 11 | 39916800 |
| 12 | 479069574 |
| 13 | 6227020800 |
| 14 | 87181402140 |
| 15 | 1307674370040 |
| 16 | 20922977418841 |
| 17 | 355687428096000 |
| 18 | 6402388104196400 |
| 19 | 121645100408832000 |
| 20 | 2432903379962038320 |
| 21 | 51090942171778378800 |
| 22 | 1124000886592995642000 |
| 23 | 25852016738884976640000 |